The invention concerns room air conditioning and filtration equipment, and in particular is directed to a unit that can operated in a positive pressure mode, a negative pressure mode, or a normal mode. The invention is also concerned with units that clean and condition the room air as well as remove or kill airborne pathogens, and which have a mechanism for introducing make-up air to create a positive pressure or overpressure in the room relative to the outside ambient air, or exhausting some of room air to create a negative pressure relative to the outside air. At least one of the inventors is the patentee of U.S. Pat. No. 5,884,500, Mar. 23, 1999 and U.S. Pat. No. 5,987,908, Nov. 23, 1999, which are incorporated herein by reference.
High Efficiency Particulate Air (HEPA) filters are used extensively in industrial, commercial and residential applications to filter out dust and dirt from the air which can harbor harmful bacteria or other micro-organisms. These filters are capable of filtering out more than 99.99% of the particles in the air.
Recently, due to the occurrence of terrorist strikes and outbreaks of contagious diseases such as SARS, there has been a heightened concern about contaminants in the indoor air, and about the ability to exclude or confine contaminants in a given area. Also, medical services are required in sufficient capacity and of the appropriate quality to handle extraordinary events or circumstances. Each community needs to have a surge capacity plan for handling a large number of emergency patients. If a terrorist event or outbreak of disease occurs, it will become necessary to isolate at least some of the patients. Some patients will need to be isolated in a fashion to keep any airborne contaminants within a confined area to protect others from the contagion. Other patients, e.g., burn patients, will need to be protected from outside contaminants reaching the patient area. Hospitals today lack sufficient numbers of hospital rooms that can be used for isolation of patients, whereas the need to isolate patients from the general public or from one another is critical in controlling the situation, whether the patients are in surge capacity facilities or in traditional hospitals.
Most hospitals today have only a few isolation rooms out of the hundreds of patient rooms in the facility. One reason for this is because isolation rooms are very expensive to build because they conventionally require separate, independent HVAC systems for each room to prevent the spread of contaminants to other areas of the hospital. In those cases where the patient is susceptible to contaminants, the room must operate at a positive pressure, whereas when the patient is infected with a contagious pathogen, the room must be under a negative pressure to protect other patients and hospital workers. However, even with isolation HVAC systems the rooms are not easy to convert from positive pressure to negative pressure or vice versa. These rooms are generally built either for positive pressure only or for negative pressure only, and this limits the flexibility of a hospital to deal with emergency situations.
Other applications could include laboratories within a hostile environment that may need a positive pressure, e.g., in a paper mill. Other examples include museum archiving rooms that need a positive pressure.
The inventor herein proposes to convert a room air conditioning unit, similar in some ways to the type described in the above-mentioned U.S. Pat. Nos. 5,884,500 and 5,987,908 to be suited for use in converting a standard, typical hospital room to an isolation room, and which can be provided with neutral pressure (equaling outside air pressure), a negative pressure relative to outside air pressure, or a positive pressure relative to outside air pressure.
These units, known commercially as HEPAir units, are used extensively in clean room situations to control airborne contaminants while maintaining temperature and humidity control for critical processes such as the sterile packaging of medical devices or pharmaceuticals. These units are also used extensively in the manufacture of semiconductor devices. These are not simple portable air conditioning units, but are industrial in nature and capable of handling relatively large volumes of air against a high static pressure such as that encountered with high efficiency particulate air (HEPA) filters, and are capable of attaining an air exchange rate that is sufficient to assure dilution and purge.